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RoleofLadleRefiningandVacuumDegassinginRailroadWheelSteel
Cleanliness
Cameron Lonsdale & Jay Galbraith Standard Steel, LLC Burnham, PA, USA
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RecentCapitalProjects• Projectstotalingmorethan$60MUSD
• Steelmaking
– Newbasicelectricarcfurnace
– Twin-tankladlerefiningandvacuumdegassingstaCon
• SynchronizedInclinedRotaryDishingPress(SIRD)InstallaCon
• Goals:Produceultra-clean,low-stress,high-precisionwheels
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MeltShopInstallaAonUpdatePhase1ofprojectcompletedattheendofDec2013:
• RevampedElectricArcFurnace(conCnuedacidpracCce)
• Replaced30MVAtransformerwitha50MVA
• Installednewwatercoolingsystem&baghousewasupgraded
• Installednew110-toncrane
Phase2completedJan2014-2015:
• Twintankladlerefining/vacuumdegassingfacility
• Slagrakesystem
• Change-overtobasicsteelmakingpracCce–January2015
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Twin-TankLFVDStaAon
TwostaConaryvacuumtanks
Ladlefurnaceroof(forheaCng)swingsbetweentanks
Twogantrycarvacuumcoverlids
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LFVDStaAonswithladlebeingheatedVacuumcoverlidmovesintoposiCononrails
Chuteforaddingalloysviaconveyorsystem
Ladlefurnaceroof(heaCng)
Pulpit
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MaterialHandlingSystem-PreciseAlloyAddiAons
Alloystoragebins
Weighinghoppers
UpperconveyorsystemfortransporCngalloystoladle
Lowerconveyorsystem
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SteelCleanlinessImprovements:ImplicaAonsforHeavyHaulWheels
• Wheelsaresubjecttoadynamicloadingenvironment-impacts
• Forsteelswithsimilarstrength(i.e.,hardness),dynamicfracturetoughnessisastrongfuncConofthesteel’scleanliness,micro-porosity,andmicrostructure
• Underheavyaxleloads,rimfaCguecrackscaniniCateinternallyatstressconcentraCons(i.e.,voidsandinclusions)
– Hardoxideinclusions,primarilyalumina,arelikelysourcesofiniCaCon– InterdendriCcsulfidesreduceducClityandtoughness
• EvidencesuggeststhatsteelswithahighdegreeofcleanlinessarelesssuscepCbletoshaberedrims&rollingcontactfaCgue(i.e.,shelling)
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SteelCleanlinessImprovements• VerificaConbytwomethods:
– ASTMStandardPracCceE1245(average&worstfieldarea%’sofoxides,voids,&sulfides)BasisforAARspecificaCon.
MeanVolume%Voids+Oxides
MaximumVolume%
Voids+Oxides
MeanVolume%Sulfides
MaximumVolume%Sulfides
0.0095% 0.150% 0.137% 0.365%
0.0073% 0.045% 0.120% 0.224%
23% 70% 12% 39%
OldSteelmakingProcess
NewSteelmakingProcess
%ImprovementwithNewProcess
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SteelCleanlinessImprovements– AutomatedSteelCleanlinessAnalysisTool(ASCAT)
• Basedoncomputer-controlledscanningelectronmicroscopy• ProvidesdetailedsizedistribuConandchemistryinformaConofinclusionsinsteel
• HasbeenshowntoprovidegoodcorrelaConwithultrasonictestdata
• DevelopedbyUSSteel,CarnegieMellonUniversity&RJLeeGroup
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ASCAT• Samplesaretakenfromtheladle• GivesinformaAononnumberofinclusions&areafracAonofinclusionsinthesamples
• ProvidesinformaAononspecificinclusiontypesandchemistry
• Notjust–“Oxide”butspecifictypeofoxide
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ASCAT• NumberDensity–Thecount(number)ofinclusionsseenbythecomputeronapolishedsteelsamplesurfaceintheareascanned.
• AreaFracAon–Theareapercentageofthepolishedsteelsamplesurfacethatisinclusions,andnotsteel
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SteelCleanliness• Removalofoxidesthataredeleterioustodynamicfracture
toughnessandrollingcontactfaCguerequiretherightcombinaConofslagchemistryandslag/metalinteracCon
• MostnotableisthepresenceofsmallerandfeweraluminainclusionswhichresultsingreaterresistancetofaCgue&fracture
• ReducedareafracConandnumberdensityofinclusions• Hydrogenismeasured,andcontrolledwithdegassing
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NewSteelmakingPracCceResults:ImpactonSulfideInclusions
• SimilarareafracConofsulfides,buthighernumberdensity→sulfidesaresmaller.
• Wearenowre-sulfurizingtohelpinsuremachinability–Sulfurassistsmachining
• Finishboring&treadturningdownstream• Sulfidecontentcouldbemademuchlower
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NewSteelmakingPracCceResults:ImpactonSulfideInclusions
• 17%moresulfideinclusionsinthe1to2.5micron(SMALL)rangeforsteelproducedusingthenewpracCce.
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ImprovementinSulfideMorphology
• Evenatthesamesulfurlevels(tomaintainacceptablemachinability),thenewsteelmakingpracCceresultsinsmall,globularsulfideswithacompletelackoflarge,eutecCcsulfides.EutecCcsulfidestendtoreducetensileducClityandtoughness.
OldPracAceNewPracAce
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NewSteelmakingPracAceResults:ImprovementinMechanicalProperAes
• RoomtemperaturetensiletestdataofAARGradeFaxles
• CleansteelmakingpracCceswithimproveddeoxidaConpracCcesresultsin:
– Finer-grained– Slightlyhigherstrength– HigherducClity
Tensile Strength
(ksi)
Yield Strength
(ksi) %
Elongation %
Reduction in Area
ASTM Grain Size #
Old Steelmaking
Process 98.1 56.9 22.9 44.9 7.0
New Steelmaking
Process 98.7 57.9 24.8 48.8 7.8
Improvement: 1% 2% 8% 9% 12%
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UpcomingTechnicalPaperatWCRR,Milan,Italy
• Kato,etal.,tobepresentedMay30–June2• Failuredata(brokenrim,AARWhyMadeCode68)of
“cleansteel”ClassCvsconvenAonalwheelsexamined• “Higherfracturetoughnesswheelswerepredictedtohave
muchlowerVSRratesthanconvenAonalwheels.”• “Higherfracturetoughnesswheelsteelsmakeitpossible
toreducetherateofVSRfailuresinwheels.”
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SynchronizedInclinedRotaryDishingPress(SIRD)InstallaAon:HigherPrecision-ForgedWheels
• Principle:IncrementaldeformaConusinganinclinedtopforgingdiethatmaintainsconstantcontactwhileboththetop&bobomdiesrotatetomaintainworkpiecestability
• Advantages:
– Closertonet-shapepriortomachining– Tighteroveralldimensionaltolerances– Rotundityandeccentricitybetweenroughboreandtread
significantlyimproved→ReducConinoverallstressstateoftherailroad
– Expectedtoresultinconsistentlylargertapesizeswithmoreuseablewearmetalintherim
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SynchronizedInclinedRotaryDishingPress(SIRD)PreliminaryResults
• Radialrun-outcontourplotsshowimprovementintheconcentricityofthehubandrimwithSIRDprocess
• Rimthicknessismoreconsistentaroundthecircumference
• Tapesizeismoreuniform
• MinimalvariaConinfrontface/backfacerimthickness&hubwallthickness
Before
Aier
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